BMW 5-Series E34 (1987 - 1996) - 1989 535i sport concerning diff noise

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Sat 5 Apr 2008 20:02
1989 535i sport concerning diff noise - thomp1983
evening folks, ive stripped the rear axle off my 1989 535 sport so i can go about replacing some of the bushes. whilst it's all removed ive took the diff out with thoughts to clean it up and paint it silver to make any future leak spotting easier. whilst ive got it on a bench if i rotate the front prop flange once per full rotation there is a noise, im quite sure it's a metallic noise (being pessimistic here, it could just be air bubbles popping in the oil), my first instinct is to remove the prop flange and check the inner gears for signs of breakage and run a magnet round to see if i can find any lose fragments. my question is does anyone have any idea to a possible cause of the noise? and secondly what is the torque figure for retightening the front prop flange nut?

cheers
chris

Edited by Dynamic Dave on 05/04/2008 at 21:13

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Sat 5 Apr 2008 20:33
e34 535i sport concerning diff noise - Number_Cruncher
If it's quiet when in the car, leave **well** alone.

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Sat 5 Apr 2008 21:09
e34 535i sport concerning diff noise - thomp1983
it does drive fine in the car, but surely the noise still shouldn't be there regardless?

chris
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Sat 5 Apr 2008 22:27
e34 535i sport concerning diff noise - Number_Cruncher
The sun and planet gears that form the differential part of the final drive aren't usually set up in a tight mesh - they don't need to be. It's quite possible that a planet is moving around on the cross shaft once per rev.

Another possibility is if they still use a reed switch for speedo sensing.

Taking the pinion flange off when you don't need to is an excellent way of making a quiet gear pair into a noisy one. I can't offer better advice than to leave it well alone.

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Sat 5 Apr 2008 22:28
e34 535i sport concerning diff noise - Number_Cruncher
Sorry - I've just re-read the age of the car concerned; for some reason, I thought the car was newer - it is probably the reed switch clicking.

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Sat 5 Apr 2008 22:43
e34 535i sport concerning diff noise - thomp1983
it's ok after further reading it's possible the noise is drag between the components, im just going to drain it fill it with new synthetic oil as synthetic doesn't require the lsd additive and then wire brush it clean and paint it with silver hammerite

chris
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Sat 5 Apr 2008 23:00
1989 535i sport concerning diff noise - pointlesspoints
I thought the reed switches worked only when liven up with power. So it should not make a noise until it has power ?
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Mon 7 Apr 2008 10:34
1989 535i sport concerning diff noise - Hamsafar
They will only 'work' electrically when powered, but they are still fundamentally mechanical, which why you can here them with no power.
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